Pneumatically-operated percussive hand tool



2 SheetQ-Sheet 2 C. H. STEVENS PNEUMATICALLY OPERATED PERCUSSIVE HANDTOOL Filed Oct. 20, 1924 March 15, 1927.

lnvenl'or 'len'zenl' E \YZPuem" j WM FM .Eiibrney Patented Mar. 15,1927.

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CLEMENT HENRY STEVENS, OF. HIGH WYCOMBE, ENGLAND.

IPNEUMATICALLY-OPERATED PERCUSSTVE HAND TOOL.

Application filed October 24), 1924, Seria1 No. 744,726, and in GreatBritain September 1924.

.This invention relates to pneumatically operated percussive hand toolsand has for its object to provide an improved construction thereof, andin particular an improved construction and arrangement of the valves forsuch tools. 7 I V 7 According to the present invention the disc valvewhich works in a chamber -be tween ported seatings is mounted in a valvebox consisting of a valve chamber formed as an aperture in a spacingdisc locatedor sandwiched between a pairiof ported discs or valve seatsenclosed between housing discs or members, the latter being providedwith lips, flanges, or equivalent projections for centralizing theenclosed discs. A ,suit able dowel pin may be provided to assist inaccurately assembling the parts and ensuring that the ports in the discsand housings are in'the correct register. I

An ejector device may be provided in the lower or one of the housings,the said ej ector' being blown or operated by a jet of air passingthrough a suitable port and 2. connecting passage, the said e ectorbeing so ar' ranged and operating as to withdraw air from between thepiston and the snap or tool on the striking stroke and thus preventcushioning taking place by compression of the air between the saidpiston and the tool or snap.

One construction of pneumatic hammer or hand tool embodying the presentinvention will now be described with reference to the accompanyingdrawings, wherein,

Fig. 1 is a plan of the valve housirfgs,

Fig. 2 is a section on line 22 of Fig. 1.

Fig. 3 is a section on line 3-3 of Figs. 1 and 2. r

Fig. 4c is a section on line 4-4. of Fig. 1.

Fig.5 is a section on line 55 of Fig. 1.

Fig. 6 is a section on line 66 of Figs. 1 and 5.

Fig. 7 is a longitudinal section of the complete tool.

Figure 8 is a longitudinal section taken through the assembled tool andhandle on an enlarged scale. Figure 8 is also a hori-' zontal sectionsimilar to Figure 2, but showing the valve in the opposite position, thecourse of the air being indicated by the arrows.

Referring now to the drawings, the valve box or chamber consists of anupper hous ing disc or member a a distance piece or spacing disc (2having a circular hole in its centre forming the valve chamber a inwhich the distributingvalve, consisting of a plate 1), fits loosely andis free to work up and down and to seat itself either on the upper orlower valve seats formed by the discs 0 c.

The said valve seats 0 0' and the distance piece dare kept concentricand held in ,position by lips f and f formed on the upper and lowerhousings a and b.

A'dowel pin t,Figs. 2 and 4, is provided to hold the different parts intheir relative positions. v

Air ports 9 and g Fig. 5, are provided to carry air under pressurefronil any suitable source of supply to the under valve face,

and air ports j and j, Fig. 6, serve similarly to carry air underpressure from the lower valve face to the .worlring cylinder of. thehammer or tool behind the piston Similarly, air .ports Z Z, Fig- 1 andFig. 4 carry air under pressure to the upper valve face and ports m andm Fig. 4', carry airunder pressure from the upper valve face via port a,Fig. 4:, to the air passage 0 in the cylinder to the underside of thepiston y at m, Fig. 7.. a

a An ejector 1", Fig. 2. is provided in the lower housing 6 adapted tobe blown orioperated by a jet of. air passing through the small port 9,Fig. 2, and the suction hole 8, Fig. 3, passes-from the port a, Figs/3and 4:,

into the chamber-of the ejector.

The valve box comprising the b'eforementioned assembled discs andhousings is lower valve face thereby raising the valve as in Figures 6and 8 and thence via ports 7' and y" to the cylinder driving the piston3 Fig. 7 forward and causing it to strike the snap or tool in the usualmanner, the rear edge of the piston 3 uncovering the exhaust port p andthus causing the pressure in the valve chamber below the valve to drop,the valve being then changed over by reason of the high pressure airentering ports Z and Z (Figs. 1 and 4.) The valve then being seated onits lower face, as shown in Fig. 4. high pressure air iasses from portsz and. l

via iports mandm and port it into passage entering the cylinder at m anddriving the piston backuntil the exhaust port 29 is open by the edge ofthe piston which thus causes the pressure in the valve chamber to drop.The valve then changes over to itsoriginal position against the uppervalve face by reason of the high pressure air entering the lower face byports 9 h and g 1-0" h and the operation is continuously. repeated. V

The. ejector 'l) is arranged to draw air from between the piston and the'tool via ports 0 s and port it on the forward or strikinggstrokecompressed air. flowing from the under: SlClQ of valve V through passageQ,

' as indicated by the arrows, and exhausting the air in space 23 andports 0,8, and thus prevent cusnioning byoonipressed air taking placebetween the piston and-theisnap.

The jet hole 9 from the lower valve face to the ejector is closed by thevalve during the. return stroke of the piston,v Fig. 2.

\Vh-at I claim as my invention and desire :'to secure by Letters Patentis:-

1. A pneumatically operated percussive hand tool comprising thecombination of a cylinder, a piston, a handle and a valve box comprisinga disc valve, an annular spacing disc surrotmding said valve, a pair ofremovable ported valve seats enclosing said valve and annular spacingdisc and consisting of 'flat plates having ports consisting of simplethrough holes, a pair of ported valve housings provided with flanges ontheir outer cireumterencesfor surrounding and centralizing said portedvalve seats and annular spacing, disc, the ports opening on the innerfaces of the said valve housings coinciding withthe ports in the fiatplates forming the renewable valve seats, means for admitting airundervpressure to said valve boX and conevy'ing said air to the requiredports in the cylinder.

2. A pneumatically operated percussive hand tool comprising thecombination of a cylinder, a piston, a :handleand a valve box comprising.a disc valve, and annular spaclIl disc surrounding said valve, a pairof removable ported valve seats enclosing said v-alve and annularspacing disc and consisting'of flat plates having ports consisting ofsimple through holes, a pair of ported valve housings provided withjfiangeson} their outer circumferences for surrounding and centralizin"jthe said'nort'ed valve seats and annular spacingdisc, the portsopening on the inner faces of the said valve housings coincidingfwiththe ports in the fiat plates forming the renewab'le'valve seats, meansfor admitting air under pressure to said valve the cylinder and to theejector in the valve box housing.

CLEMENT HENRY srnvnns;

